The problem I wrote about a day or two ago has now been resolved. In an effort to minimise server memory usage, I have a means of making sure code is only loaded as and when it is needed. As a basic example, there’s no need to load all the stuff related to displaying videos on every page – just the video page. This process appears to have suddenly started behaving a bit overzealously and actually prohibiting code from loading that is very much needed. I have found a solution to this and am once again able to generate products (prints) from new additions to the gallery.